Dehydrated alfalfa is used as a supplement in livestock feed. The dehydrated alfalfa is customarily obtained by a process which involves harvesting alfalfa, hauling the harvested alfalfa to a centrally-located processing plant, heating the alfalfa at the plant to evaporate moisture therefrom, and then pelletizing the alfalfa. The alfalfa is usually dehydrated in rotary kilns which are heated by the combustion of fossil fuels such as oil or natural gas. A significant amount of thermal energy is required to dehydrate the alfalfa in this manner. Hence, with increasing constraints on the supply of fossil fuels, it should be apparent that the cost to produce dehydrated alfalfa by this process will continue to bear a direct relation to the cost of fuel.
Conventionally, alfalfa to be dehydrated is harvested by a self-propelled vehicle which cuts the alfalfa and collects the same in a hopper carried on the vehicle or in a trailer towed behind the vehicle. Although this procedure has the advantage of minimizing mechanical handling of the alfalfa in the field, it requires a substantial amount of energy simply to haul the relatively heavy, moisture-laden alfalfa to the processing plant. Also, the restrictions on the physical size of vehicles which can be used to haul alfalfa on the roads makes it desirable for the alfalfa to be compacted as much as possible for hauling in order to minimize the number of trips required to transport a given weight of alfalfa from the field to the processing plant.
The amount of moisture in the alfalfa can be reduced by sun-drying or field-wilting techniques. These techniques involve cutting the alfalfa, tedding the alfalfa, and gathering the alfalfa after it has dried to the desired moisture level. Although this procedure utilizes free solar energy to evaporate moisture from the alfalfa, solar energy does not provide a reliable source of heat because of the vagaries of the weather. Moreover, this technique is also less efficient since it involves greater mechanical handling of the alfalfa and hence more labor than the conventional procedure.
It is known that mechanical handling of dried alfalfa can cause substantial field losses of valuable plant matter. For instance, as the alfalfa dries, its leaves become brittle. Brittle leaves are easily shattered by mechanical manipulation. As much as 10-20% of the alfalfa plant may be lost from mechanical handling. Also, 5-10% of the dry plant matter can be lost by respiration after cutting. Since the leaves are an important part of the alfalfa plant containing the most protein and the least fiber, it should be apparent that these losses should be avoided where possible.
In addition to the losses due to mechanical handling, sun-drying of alfalfa is known to cause a deterioration in the carotene and xanthophyll content of the alfalfa. These components, together with protein, are normally guaranteed in the analysis of dehydrated alfalfa. Accordingly, it should be apparent that a process whereby a high-quality dehydrated alfalfa product can be produced efficiently is highly desirable.
In recent years, some experimental work has been conducted to demonstrate the practicality of processes for extracting protein concentrates from the alfalfa plant. In these processes, harvested alfalfa is transported to a processing plant where the alfalfa is macerated and pressed to separate the alfalfa into a fibrous fraction and a liquid fraction. The fibrous fraction is retained and dehydrated or used as ensilage, etc. The liquid fraction is heated to a predetermined temperature to cause the plant protein contained therein to coagulate and form a cheeselike curd which floats on a whey or brown juice. The curd is rich in protein, low in fiber content, and high in xanthophyll and carotene. The curd is, therefore, economically valuable as a feed supplement for non-ruminant animals, and especially poultry. For a more detailed description of the above processes, reference is made to the following articles: Crops and Soils Magazine, August-September, 1973, pages 12-13; Report of Fifth Annual Alfalfa Symposium held on Apr. 8, 1975, in Hershey, Pa.; Technical and Ergonomic Aspects of the Production of Alfalfa Silage by Fractionation, paper given at the Eighth International Congress of Agricultural Engineering held in The Netherlands on Sept. 23-29, 1974, by Bouhn, Koegel, Schirer, and Fromin; and a Report entitled On the Farm Producion of Alfalfa Juice Protein by Bouhn and Koegel presented at the American Society of Agricultural Engineers Plant Juice Seminar at Madison, Wisconsin on Apr. 27, 1974.
Although the processes described in the above articles are capable of extracting valuable components from alfalfa, they have several limitations. For instance, the processes are performed at a stationary plant location. Thus, the alfalfa (ard the water contained therein) must be hauled to the plant, and this involves the expenditure of substantial amounts of labor and energy. In addition, these processes generate substantial quantities of deproteinized brown juice or whey which must be discarded in an environmentally-satisfactory manner.